In a system in which messages are transmitted from a fixed transmission network to a plurality of radios on an individual basis, such as a paging system, it is sometimes desirable to send a common message or common command to all the radios currently active within the system. This situation is herein termed a global event. Examples of such global events are an all call information message (e.g., a time update or a new software download) and a command directing all radios to alter an acknowledgment mode from synchronous to asynchronous. In some radio communication systems, such as paging systems, the plurality of radios are each in a receiving mode at unique predetermined times during a defined radio transmission cycle. One use of unique predetermined times is to provide battery longevity in a selective call radio communication system, by allowing each radio to be in a low power mode for a large percentage of time, except when one or more messages are queued for delivery to the radio. Another use of unique predetermined times is for sending different information at different successive periods to each of individual radios or groups of radios having no selective call addresses. In such systems, a known means of delivering a global event is to send the global event in every unique predetermined time or successive period. However, this approach involves sending the global event information repetitively, and therefore reduces throughput in the system. The reduction can be very significant in systems having large numbers of unique predetermined times or successive periods.
A technique is described in laid open Japanese Patent Application 3-170755, having a laid open date of 16 Apr. 1993, which is for use in Post Office Code Standardization Advisory Committee (POCSAG) radio systems. The technique uses a special batch sequence which allows for the transmission of control information, beginning with a notification sequence. The notification sequence begins with the transmission of the system ID as the first address code word of each frame in a batch of eight frames. Since the system ID is a reserved address code word, only nationwide pagers respond to the system ID. Following the system 1713 a notification address code word as the second code word in each frame of the notification sequence. The notification address code word is also a reserved code word like the system ID. Once all nationwide pagers have been notified that control information is to be transmitted in the following batch, all nationwide pagers, regardless of which frame the pagers are assigned, begin receiving the overhead data starting in the first frame of the next message batch. The overhead data provides specific system related information which is used to improve the scanning efficiency of the nationwide pager. The technique, although useful for sending control information to all active nationwide pagers in a paging communication system, is less efficient than desirable for other systems because all words in a batch are used for conveying the notification, and the technique is restrictive in that only nationwide pagers are able to be notified.
Thus, what is needed is an improved technique for efficiently communicating a global event to all active radios in a radio communication system in which the radios are in a receive state during a predetermined portion of a transmission cycle.